This invention relates in general to a method of repairing metal surfaces which have been damaged by scoring, dentin, grooving or the like and, more specifically to a repair method which comprises filling damaged areas with a metal-filled resin and plating a wear resistant layer thereover.
Metal surfaces of machine parts and the like are often damaged by wear, accident, and the like. Metal surfaces which bear against other metal surfaces during machine operation are subject to scoring and wear grooves that penetrate the surface in localized areas. Other metal surfaces may be accidentally struck, forming dents. Typical surfaces which developed these localized blemishes include the mating surfaces of pistons and inner cylinder walls in hydraulic cylinders,and other devices in which an inner member slides within a tube.
Conventionally, damaged surfaces are ground until the blemishes are removed, the entire surface is replated oversize and the surface is ground to size and polished. This is expensive, time consuming and requires excessive amount of metal to be ground away over the entire surface, even though the blemishes are localized.
Attempts have been made to fill damaged surfaces with an epoxy resin containing metal particles, as described, for example, by Griffen et al. in U.S. Pat. No. 2,984,895. These methods generally require grinding away the damaged surface to provide depth to the repair area and to promote adhesion between the metal and the filled resin. These methods tend to suffer from short repair life, due to a relatively soft wear surface that wears rapidly and failures of adhesion of the repair to the base metal during use.
Others have tried grinding away and knurling the area to be repaired, spraying a coating of metal onto the repair surface and machining the surface to the original configuration. While these repairs may be acceptable for short periods, the characteristics of the sprayed coating are such that wear tends to be rapid. Typical of such methods is that described by Timuska in U.S. Pat. No. 3,004,336.
In particular, hydraulic cylinders are often subject to scoring, grooving, etc. of the mating piston and cylinder surfaces. This localized damage leads to leaking of hydraulic fluid past the cylinder and inefficient operation. A quick, convenient and effective repair for such damage is particularly needed in the hydraulic cylinder field.
Thus, there is a continuing need for improved methods of repairing damaged or worn metal surfaces, such as hydraulic pistons and cylinders which can be rapidly and economically accomplished, provides improved adhesion of the repair material to the damaged surface and provides a tough, long-wearing repaired surface.